Lots of variation of the 'permanently' attached measuring rods. Many attach to the bar nut. The ones above appear to mount via the handle mounting screws. I suppose that you could mount some type of bracket there, that still let you quickly mount and remove the actual measuring rod?
@Ontario Firewood Resource 's rod maybe could be mounted with a wing nut for quick installation and removal?
Simplest I have seen was just a metal rod with an 'L' bent into the end, that attached to the vertical section of the saw handle with radiator clamps: could pivot out of the way, if needed.
I just think that the magnet sticks are so easy; work with any saw; on either side of the bar; require no modifications to the saw; etc. I have left them on when sectioning smaller diameter limb wood, and I have removed them after marking larger logs. Let's me keep both hands on the saw.
This a good idea if you have a quick disconnect so you can use the stihl nut tool instead of a wrench. When I use mine, it doesnt get it the way and it bends when navigating the chainsaw in and around your wood pile.
Philbert